Mobuko Sonota, a third-year Tousei High School student, stands out with her pink hair and composed, friendly presence. She navigates life in an extraordinary family of seventeen identical sisters, segmented into six siblings a year younger, six two years her junior, and five her exact age—a setup that often sparks amused reactions for its sheer scale.

Her collaboration with the Tesaguri club blends practicality with whimsy, frequently recruiting her sisters to test inventive concepts. Together, they tackle challenges like baseball blindfolded with only verbal cues, football interspersed with impromptu haiku, and shogi paired with Twister-esque contortions. Though reserved during brainstorming, Mobuko occasionally contributes ideas, while her primary role lies in logistical support—organizing gear or orchestrating experiments. One notable project involved a karuta match using stealthily captured candid photos of club members, showcasing her knack for merging creativity with lighthearted mischief.

Steadfastly reliable, Mobuko’s tranquil nature balances the club’s exuberance, anchoring their eclectic endeavors through shifting seasons and varied projects. Her enduring participation underscores her quiet dedication, seamlessly integrating her familial resources into the club’s dynamic without seeking the spotlight.